The Obama administration, which has a chilling zeal for investigating leaks and prosecuting leakers, has failed to offer a credible justification for secretly combing through the phone records of reporters and editors at The Associated Press in what looks like a fishing expedition for sources and an effort to frighten off whistle-blowers. Last Friday, Justice Department officials revealed that they had been going through The AP’s records for months. The dragnet covered the work, home and cellphone records used by almost 100 people at one of the oldest and most reputable news organizations. James Cole, the deputy attorney general, offered no further explanation on Tuesday, saying only that it was part of a “criminal investigation involving highly classified material” from early 2012.

Attorney General Eric Holder Jr. said he could not comment on an open investigation — although he was happy to comment on the open investigation into the tax audits of conservative groups, which he said might have been criminal and were “certainly outrageous and unacceptable.”

Both Holder and Cole declared their commitment — and that of President Barack Obama — to press freedoms. Cole said the administration does not “take lightly” such secretive trolling through media records.

We are not convinced. For over 30 years, the media and the government have used a well-honed system to balance the government’s need to pursue criminals or national security breaches with the media’s constitutional right to inform the public. This action against The AP, as the Reporters Committee for Freedom of the Press outlined in a letter to Holder, “calls into question the very integrity” of the administration’s policy toward the press.

The records covered 20 phone lines including main office phones in New York City, Washington, D.C., Hartford, Conn., and the congressional press gallery. The guidelines for such subpoenas, first enacted in 1972, require that requests for media information be narrow. The Reporters Committee said this action is so broad that it allowed prosecutors to “plunder two months of news gathering materials to seek information that might interest them.”

Holder said the leak under scrutiny, believed to be about the foiling of a terrorist plot in Yemen a year ago, “put the American people at risk,” although he did not say how, and the records sweep went far beyond any one news article. Gary Pruitt, president of The AP, said two months’ worth of records could provide a “road map” to its whole news gathering operation.

Under the guidelines, the administration should have sought information from other sources. Cole said it did. But the administration made the troubling and discrediting decision not to inform The AP in advance. The guidelines require investigators to provide notice unless it would “pose a substantial threat to the integrity of the investigation.” That is intended to prevent destruction of evidence, an impossibility in this case.

The Obama administration has indicted six current and former officials under the Espionage Act, which had previously been used only three times since it was enacted in 1917. One, a former CIA officer, pleaded guilty under another law for revealing the name of an agent who participated in the torture of a terrorist suspect. Meanwhile, Obama decided not to investigate, much less prosecute, anyone who actually did the torturing.

The Justice Department is pursuing at least two major press investigations, including one believed to be focused on David Sanger’s reporting in a book and in The Times on an American-Israeli effort to sabotage Iranian nuclear works. These tactics will not scare us off, or The AP, but they could reveal sources on other stories and frighten confidential contacts vital to coverage of government.